Retired airline captain Chesley "Sully" Sullenberger, the pilot who became an American hero after safely landing US Airways Flight 1549 on New York's Hudson River in 2009, announced Tuesday that he has been diagnosed with early-stage Alzheimer's disease.

Sullenberger, 75, disclosed the diagnosis in a public statement, saying he plans to face the disease with optimism and the support of his family.

"Lorrie and I often said we won the baby lottery with our two daughters. And we have learned what people say is actually true: that grandchildren are a game changer. Our granddaughter gives a whole new meaning to life," he said.

"With that said, I recently found out I have been diagnosed with Alzheimer's Disease. It is early stage," Sullenberger continued.

"For now, this means a name may not come easily to me, I forget a story I have recently told, or I don't sleep as well, but I am in the beginning of this long journey."

Looking back on the emergency landing that became known as the "Miracle on the Hudson," the retired pilot said the lesson from that day still applies.

"Over the years, when people would ask about the successful outcome of Flight 1549, I would say that 'courage can be contagious,' and on that day it helped everyone band together to get everyone off that airplane successfully," he said.

"Now we need that courage to battle this disease. I am now part of a larger community with many of you, and we will be courageous together."

Sullenberger also said he intends to use the public platform he gained after Flight 1549 to bring greater attention to Alzheimer's disease.

"My doctor, Dr Gil Rabinovici with UCSF Medical Center, has opened my eyes to the prevalence of Alzheimer's," he wrote.

"This disease, he has told me, spares no age group and impacts millions of people around the world. It is the unwanted visitor at the door," Sullenberger continued.

"So this new phase of my life has challenged what it means to be of service. And the answer is to speak up. It is my hope that by sharing this, other families living in the shadows with this disease will feel they too can step forward."

According to the Alzheimer's Association, an estimated 7.4 million Americans age 65 and older are living with clinical Alzheimer's disease.

Sullenberger earned nationwide acclaim on Jan. 15, 2009, after a flock of geese disabled both engines of US Airways Flight 1549 shortly after takeoff from New York's LaGuardia Airport.

He safely ditched the Airbus A320 in the Hudson River, and all 155 passengers and crew survived. The feat was later portrayed in Clint Eastwood's 2016 film "Sully," starring Tom Hanks.

Despite the diagnosis, Sullenberger said he remains focused on the future.

"My diagnosis will not prevent me from looking forward to and appreciating our future," he said.

Sullenberger added that he will confront the illness with his wife of 37 years, Lorrie Sullenberger.

"I will navigate this chapter with my wonderful family by my side," he said.